A primary concern in any process which results in the generation of offensive odors is how to eliminate or reduce such odors and to bring them into acceptable emission levels. The unique system comprising the present invention achieves these ends in an efficient, simple and economic manner. A composing facility, like any other facility who's operation has the potential for offensive odor generation, must operate in a manner that safeguards the public health, safety and the environment. While the invention has wide application to various operating processes, it will be described and illustrated in connection with the co-composting of municipal solid waste and sewage sludge.
Most odors from a composting process result from the incomplete oxidation of organic materials, principally carbohydrates and proteins, in the feed stock. Carbohydrates contain carbon, hydrogen and oxygen in compounds such as cellulose and sugars, which under anaerobic conditions readily decompose and produce odorous compounds such as alcohols, esters, aldehydes and organic acids. Proteins contain carbon, hydrogen, nitrogen, oxygen and sulfur and can produce odorous compounds such as ammonia, amines and mercaptans. By utilizing the present invention, odor emissions from a composting facility can be controlled by the proper design and operation of an aerobic decomposition process and system which converts the odorous compounds into odorless carbon dioxide and water. Such aerobic decomposition occurs primarily in the composting process itself if proper aerobic conditions are maintained. However, it has been found that odor control by the composting process itself cannot typically be expected to reduce odors to acceptable levels. Accordingly, numerous techniques and methods have been employed in an attempt to treat or remove odorous compounds from process effluents. Such methods have included masking or covering an unacceptable odor with an acceptable one; chemical oxidation with agents such as ozone or chlorinated compounds; adsorption onto activated carbon; thermo-oxidation as by incineration; absorption by chemical solutions; or combinations of the above. These methods, on the whole, when applied to composting facilities, have not been too successful.